If it doesn't have to be the Yamaha setup you can always go with the Cobra's. I have the Cobra standard backrest. Doesn't have the quick release feature but for $249 it's a lot more affordable and my wife loves the support.
Yamaha told me that the chrome on the Quick Release Backrest Base P/N STR-5C743-10-00 that attaches to the bike was screwed up. They had to send them all back. I am also still waiting for mine. Everyone has been waiting since December. They just announced the first batch of Quick Release Backrest Bases would be sent out soon in the order that they had been purchased. They will be doing this in batches.
These 3 COBRA Passenger Backrest are currently available and in stock:
Cobra Standard Sissy Bar (17" tall) with Freedom Pad & Mounting Brackets $ 225
Cobra Short Sissy Bar (14" tall) with Freedom Pad & Mounting Brackets $ 225
Cobra Mini Sissy Bar (11" tall) with Freedom Pad & Mounting Brackets $ 225
If you need one, contact Juan at 305-255-7311 or send a PM and he will take care of you.